Vehicle steering wheel position data has application to various vehicle systems. For example, it has been proposed to utilize vehicle steering wheel position for anti-lock braking and active suspension control systems. Accurate vehicle steering wheel position detection requires an initial determination of the steering wheel center position, corresponding to the steering wheel position resulting in a straight direction of vehicle travel. Once known, the absolute angular position of the steering wheel can thereafter be maintained in accordance with the degree of rotation of the steering wheel relative to the center position.
Modern vehicles equipped with electric power steering systems have a brushless DC electric motor which provides torque assist in moving the vehicle wheels in response to rotation of the steering wheel. The amount of torque assist provided by the brushless motor is principally a function of (i) the torque applied by the vehicle operator to the steering wheel, as sensed by a torque sensor contained within the steering system, (ii) brushless motor (rotor) position data supplied by a position sensor contained within the brushless motor housing, and (iii) vehicle speed data supplied by a vehicle speed sensor.
Prior art steering wheel position detection methods require the addition of a separate steering wheel position sensor, responsive to rotation of the steering wheel, for accurately determining the steering wheel center position. Unfortunately, the addition of a steering wheel position sensor increases the cost of the overall steering system.